Electric motors have been proposed for driving the plates, such as direct current, alternate current or three-phase motors. These motors can be of the synchronous, asynchronous or stepping types. These electric motors are integrally connected to the plate by means of a so-called coupling flange, which, by being connected both to the end of the motor shaft and to the plate, or to a plate support to which the actual plate is then connected, provides a (rotatably integral) serial connection between the motor shaft and the plate.
It has been observed that the coupling flange, as it must act as the transitional element between the very small diameter of the motor shaft and the relatively large diameter of the plate, has a certain radial and axial bulk, which is further increased by the connecting members by means of which the coupling flange is connected to the motor shaft. This moves the plate away from the motor, and results in an undesired bulk for the whole motor-plate unit.
In order to resolve the problem of this bulk, it has been suggested, for example in EP 1 596 488 A2, to arrange at least a part of the connecting elements between the motor shaft and the plate within the motor housing and, particularly, to provide the connection between the motor shaft and the coupling flange within the motor housing.
This known solution reduces the distance between motor and plate, but at the same time, the axial and transversal bulk of the motor is increased, thus resulting in an overall bulk of the motor-plate unit which is still considerable.
Furthermore, both the shaft and coupling flange require a precision mechanical processing in the motor bearing areas and in the connecting areas therebetween and each maintenance activity on the connection within the motor requires the motor to be disassembled and this necessarily also involves the motor bearings.
In addition to said disadvantages, all known solutions have a drawback in that the kinematic chain of motor shaft-coupling flange-plate support-plate is undesirably long and thus yielding, because of the clearances occurring in the at least three coupling points.
The object of the present invention is thus to improve the plate motors, such as to reduce the total bulk of the motor-plate unit and increase the rigidity of the transmission of the torsion from the motor to the plate.
A further object of the present invention is to provide a motor for a plate, which does not require any maintenance activity to be carried out on the connection between the motor shaft and the coupling flange.